There are many different ways to learn!
Some people buy books and teach themselves. Others may get lessons, either on a one to one basis, or in a class. Some people don’t even bother using books or have lessons, and can still learn to play quite well.
However, if you want to learn properly and give yourself the best possible chance of playing to a good standard, then I would always recommend having lessons with a personal tutor. If you try and teach yourself, even if you use a book, then you don’t have anyone to show you where you might be going wrong.
Can you imagine if you went to school and there were no teachers, and the only way to learn was from a book? Not only would it be very boring, but you are missing out on that interaction and guidance that you need. You would also get stuck from time to time, and not have anyone to ask for help. A teacher can also keep things from getting boring, and can inspire and push you to learn.
Of course, your teacher doesn’t have to be physically in front of you – an online teacher can be just as good as a teacher in person.
Finally, I would advise taking the piano grades through the ABRSM. It’s the perfect way to learn everything you need to know about the piano. From learning scales, chords, keys; to learning which fingers to use. How to play loud and soft; how to accentuate the notes, and how to read music properly and quickly etc.
However, if you are learning from scratch and don’t know how to read music, then I would advise holding off on piano grade lessons lessons until you can. Learning to read music can be done solely from a book to start with, and shouldn’t take very long. Once you’ve also got a decent grasp of the notes on the piano as well, then you should be good to go with the lessons.
There’s nothing to stop you jumping straight in with the piano tutorial videos – and I strongly recommend learning the piano blues from these, alongside the classical curriculum at formal piano lessons which will help you improve your technique.